The primary purpose of this study is to compare the bioavailability of an experimental intravenous formulation to the approved oral formulation of the immunosuppressive drug, mycophenolate mofetil. Oral MMF started within 72 hours after transplant in combination with cyclosporine and steroids was shown to be safe and effective at preventing renal allograft rejection and was recently approved for that use. There are certain instances in which oral medication cannot be given to a patient, such as immediately after renal transplant, after liver or pancreas transplantation, or in the case of ileus or severe nausea and vomiting. Patients with these conditions cannot therfore receive MMF and may be at increased risk of rejection. Other immunosuppressive drugs, such as azathioprine cyclosporine and steroids are available in the intravenous form and are used when indicated. The safety of IV MMF is being more completely analyzed in a separate study in which we participated. There have been no major toxicities seen.